My '98 5.4 has had all the coils replaced over the past couple of years; ea. time giving me a CEL when it stared missing. Now it's missing again; no CEL's and no errors when hooked up to a high dollar Snap-On reader. Really don't want to start replacing the COP's one at a time. Any suggestions ?
Can the Snapon reader diagnose a bad plug?
It can, but it not detect a miss, so no cyl. Was called out as misfiring
What functions are you using on the scan tool? Between misfire counters and power balance, the only way you wouldn't identify the misfiring cylinder is if it wasn't currently misfiring.
I would say if your truck posted misfire codes every time a problem cropped up and replacing the coil fixed the problem every time, you've been very lucky on that. Usually much more diagnosis is required than just checking the DTCs.
When is it missing?
Frequently at idle, hard miss under load. reply to Kenny_McCormic:
Plugs done recently?
Plug wire, almost 100% one is faulty.
Grab a replacement one and rotate them until you find the bad one.
In the 1% chance it is not the wire it will be one of the coil packs.
Open hood with engine running at night, you may see the coil pack arcing.
I have had dozens of these engines, it is common
Yeah, that's a plug, wire or coil, I'd eliminate in that order, start with new plugs.
The ones with COP don't have wires.
If the scantool being used can check EITHER misfire counters in datastream or power balance in 'special functions/tests' it would identify the problem cylinders.
If you want to start trying to diagnose 'manually' you could have someone power brake it in gear enough to make it miss consistently and then unplug coils or injectors one at a time (reconnecting before moving to the next) and looking for the one that DOESNT make the engine run worse (that'll be the one contributing the least), or you could try to make it miss continually and check the temperature at each exhaust port with an IR pyrometer and look for the cooler cylinder.
In reply to Vigo:
I think aussiesmg is talking about the coil spring between the plug and coil inside the boot. If that were to break you'll have a problem. Based on how rockauto seems to offer more boot/wire kits than they do complete COP units I'd guess it is a failure prone part as he states.
98 has plug wires, the went COP around 02
Thanks I'LL see if another brand of reader can I'd the missing cyl. Still wonder why no cel !
In reply to Vigo:
My 98 5.4 triton has cop's. all have been changed over the past several years
reply to aussiesmg:
My dad spent time and $$ replacing ignition coils and injectors trying to fix a miss in his 5.4 Expedition. No progress until I suggested he check the plugs... one of them was loose.
When my '99 truck started misfiring, I went directly to Oreillys and used their scanner. Diagnosed the #6 COP correctly.
Rog
Yeah I forgot, damn Ford and their staggered engine releases, 98 was the first year of COP not 02
Mmmmhmm.. anyway, if you dont actually have a scantool and are relying on $8.50/hr parts store employees operating a code reader, then yeah, you are going to have to do things 'the hard way'. Just keep in mind if you go the route of manually checking 'power balance' by unplugging things while the engine is running, you WILL set a whole bunch of codes that will need to be erased at some point. The point and shoot thermometer testing is 'non invasive' but does require you to have a tool you may not have. Cheap ones are $15-30 these days.
Hokie69 wrote: My '98 5.4 has had all the coils replaced over the past couple of years; ea. time giving me a CEL when it stared missing. Now it's missing again; no CEL's and no errors when hooked up to a high dollar Snap-On reader. Really don't want to start replacing the COP's one at a time. Any suggestions ?
If you cleared the check engine light recently, the computer probably didn't get a chance to do a cylinder balance relearn, and as such it won't set a misfire code even if you yanked a coil entirely off the engine.
Fords suck at misfire. And the only data you can get is misfire history in Mode 6, sometimes.
In reply to Knurled: Will get a new set of plugs installed as soon as possible. Will also check the coil spring. Thanks for the responses. Wish I had a 5.0
Ugh, as bad as the Mod motors can be sometimes, I do NOT miss having to work on the 5.0/5.8 engines. Intake coolant leaks, timing covers that corrode away, oil pans that rust through (well, I guess some things don't change), and it's all buried under a mass of failure prone air injection/EGR plumbing and control in order to limp a 60s engine design through 90s emissions requirements. Don't miss 'em.
was this one of the 5.4's that shot the spark plugs out at random times?
If you cleared the check engine light recently, the computer probably didn't get a chance to do a cylinder balance relearn, and as such it won't set a misfire code even if you yanked a coil entirely off the engine.
Yeah, a Ford can be missing like crazy but for some reason it wont post a misfire code until it has run ALL of its OBDII monitors, which can take days of driving. But when coils fail they can also set P0350s coil primary circuit codes which im not sure whether they will pop instantly or not. I think they do. But that only covers some tiny percentage of actual cases, probably.
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